The present invention relates to a device for loading and unloading a pig into or out of a pipeline, comprising an attachment piece having an interior space, with an end-side access point into the interior space and an outlet leading in the direction of the pipeline or into the latter, wherein the interior space is able to be brought into fluid communication with the pipeline, in particular an oil or gas pipeline.
Prior art of the generic type for loading and unloading a pig is known from U.S. Pat. No. 8,616,074 B2. In said document, a device that is configured in the form of a Y piece has in the figures an attachment piece, which is connectable or connected to the Y piece on one side via valves and to the further pipeline on the other side via a kicker line. A guide element for receiving a pig can be moved via a drive means in the form of a threaded rod into the region through which primary flow takes place, and can be moved into or out of the latter in order to discharge or receive the pig, respectively. In this operating state, the interior space of the attachment piece is in fluid communication with the pipeline on account of being flowed through by the medium flowing in via the kicker line. Thus, on account of the drive means, a further access point into the pipeline or into the Y piece has to be sealed off.
In this device and in other prior art devices of similar construction, an additional opening in the pipeline is also necessary for the kicker line. Via said additional opening, the rear of the pig is subjected to pressure by the medium located in the pipeline in order to travel into the pipeline.
In addition to the risk associated with the opening in a second region of the pipeline, the device according to U.S. Pat. No. 8,616,074 B2 is also of relatively large construction, and this may be problematic in particular in pipeline systems present in industrial plants. At the same time, insertion into and removal from the line can be problematic, if the guide element and inner wall of the Y piece do not allow reliable sealing with respect to the pig or to the discs and cups thereof. As a result of excessive pressure drops on account of medium flowing past, the movement of the pig cannot be ensured one hundred percent.